How to defeat a dragon with math - Garth Sundem

4,576,168 views ・ 2013-01-15

TED-Ed


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Translator: Andrea McDonough Reviewer: Bedirhan Cinar
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Once upon a time
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in the magical and very round Land of Pi,
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there lived six swashbuckling musketeers.
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There names were Parentheses,
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Exponents,
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Multiplication,
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Division,
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Addition,
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and Subtraction.
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But each was known best by his or her mark:
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the two hands ready to catch a fly of Parentheses,
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the small and raised digits of Exponents,
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the mighty X of Multiplication,
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slash of Division,
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plus of Addition,
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and, well, you can guess the symbol
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by which little Subtraction was best known.
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The Land of Pi was not necessarily the most peaceful place,
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and that's why the numbers of the kingdom
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needed the musketeers.
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The Land of Pi had been ruled by the numbers
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as anarcho-syndicalist commune,
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each number with a vote,
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but, one powerful number from what we'll call the Imperial Senate,
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engineered a war between some robot things
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and the knights of the kingdom,
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and then installed himself as Supreme Emperor,
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and then Puff the Magic Digit Dragon ate him,
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and a princess or two,
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and, well, all the other numbers in the Land of Pi actually.
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It was kind of a big day.
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Anyway, the musketeers were called to action
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to save the Land of Pi from the voracious dragon.
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They rode towards him on their valiant steeds and attacked.
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First Multiplication,
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then Parentheses,
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but that didn't work.
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The dragon continued eating people.
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So Addition tried, but was thrown aside.
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Exponents leaped at the beast
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and was quickly squashed.
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Nothing was working.
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The musketeers huddled and formulated a plan.
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They would attack in sequence,
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but who should go first?
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They bickered for a while,
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the dragon ate a few more princesses,
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and then they finally agreed.
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They jumped into the first, smallest parentheses
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inside the great Puff the Digit Dragon.
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Parentheses pointed out where to work first
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and protected Exponents, Multiplication, Division,
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Addition, and Subtraction
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while they diced and sliced.
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First here,
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then, move over there,
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then there.
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Look out! There's another set!
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Parentheses pointed and Exponents took the lead.
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Then, it was Multiplication, Division,
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Addition, and Subtraction, each in turn,
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always the same order.
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P-E-M-D-A-S
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When they finished that set, they went to another,
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and another,
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always working inside the parentheses in PEMDAS order.
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Pop! Pop! Pop! Pop! Pop!
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PEMDAS, there is another spot!
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Don't forget, there can be parentheses inside parentheses.
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There's one!
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And that tricky exponent.
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There we go!
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Finally, the PEMDAS Musketeers had whittled Puff
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down to his last fearsome roar.
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But, having vanquished Puff the Magic Digit Dragon,
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all the empire's numbers sprang again from this tiny little number one,
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and they all lived happily ever after.
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Except for the Emperor Number,
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which they threw into the mouth
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of an ancient nesting creature in the desert.
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The End.
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